Friday, 26 April 2013

Reinhart and Rogoff: responding to criticisms

Last week, three economists at the University of Massachusetts, Amherst, released a paper criticizing our findings. They correctly identified a spreadsheet coding error that led us to miscalculate the growth rates of highly indebted countries since World War II. But they also accused us of “serious errors” stemming from “selective exclusion” of relevant data and “unconventional weighting” of statistics — charges that we vehemently dispute.

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The academic literature on debt and growth has for some time been focused on identifying causality. Does high debt merely reflect weaker tax revenues and slower growth? Or does high debt undermine growth?

Our view has always been that causality runs in both directions, and that there is no rule that applies across all times and places.

These critics, Thomas Herndon, Michael Ash and Robert Pollin, identified a spreadsheet calculation error, but also accused us of two “serious errors”: “selective exclusion of available data” and “unconventional weighting of summary statistics.”

We acknowledged the calculation error in an online statement posted the night we received the article, but we adamantly deny the other accusations.

They neglected to report that we included both median and average estimates for growth, at various levels of debt in relation to economic output, going back to 1800. Our paper gave significant weight to the median estimates, precisely because they reduce the problem posed by data outliers, a constant source of concern when doing archival research that reaches far back into economic history spanning several periods of war and economic crises.

When you look at our median estimates, they are actually quite similar to those of the University of Massachusetts researchers.